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prop savers for 5mm shaft?

GLuft3

Junior Member
#1
My son, Nick, and I built an FT Tiny Trainer from plans and bought a power pack and accessories to go with it. The EMAX MT 1806 motor runs great, and we maiden'd it this past week. This was our first build and first time flying, and it has been a blast. At age 10, Nick is a natural pilot.

Of course, we blew through two 6x3 props really quickly, but we've been having fun using it as a chuck glider. I haven't even bothered building the 3-channel polyhedral wing.

Then I remembered that the FT Mini Guinea that we bought for our next project has the same motor and props! So, once we figured out what the "R" in 0603R meant, ;-) we were back in business. At least for a few minutes until we severed an alieron servo control line and had to repair that. Today's torrential rains have kept us from breaking the remaining two borrowed props, but I was wondering if there's a better way.

The guy at our LHS does not have any 6x3 props in stock :-( He suggested that we get prop savers, but we can't seem to find any that fit the 5mm shaft, so I'm wondering if that's even an option for what are essentially quadcopter motors.

I'm not sure why the specs for the MT1806 say it has a 2mm shaft--nor what the included allen wrench is for.

Alternatively, we might want to build landing gear and no longer fly this as a belly lander... But I don't know how well that works in the mud and grass--or for nose-down attitude mishaps.

Puzzled n00bs in Connecticut.
 
#2
The problem with prop savers on those motors is they are high kv, really small, and the props are extremely cheap. I personally haven't seen prop savers in that size either. The reason the motor says it has a 2mm shaft is because the top of it is a 5mm prop adapter, but on the inside it is 2mm. I think the allen wrench was for mounting screws, but I'm not sure. I'd go ahead and tinker with that landing gear idea, shouldn't be too hard to make.
 

Craftydan

Hostage Taker of Quads
Staff member
Moderator
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#3
The reason Prop savers stop around a 3mm shaft is power -- put more than ~100W of power into the prop and it has too much energy for the band to reliably hold it on, yet give enough not to break the prop when hit. I use pretty stout silicone bands and I've got one power system capable of ~150W that uses one . . . and will blow out the band occasionally on a WOT punch (and I get to buy a new prop not because it's broken, but because it's lost :p )

That being said, the mid-to-small 250 multirotor motors (like the 1806's) don't all pull that much power -- on 3S they can get pretty close. The 5mm threaded prop adaptor built into the motor bell is designed to fit the props exactly, because a multirotor needs a tight connection between prop and motor -- the subtle changes in motor speed in a multirotor don't tolerate well the slop from a prop-saver band . . . but for your use, that's not an issue for you. Unfortunately, this is the reason you won't find a threaded 5mm propsaver, unless you machine one yourself. Might be possible to jury-rig one with an M5 wingnut -- if you can find one locally -- but you'll probably need to balance and loc-tite it on, and I'd recommend using donuts cut from silicone tubing for the bands, not the typical O-Rings.

. . . Alternatively . . . .

- Switch to another motor. There are plenty of other motors that will drag around a tiny trainer that *HAVE* prop savers, but this can run you ~ $10-20 online. The ESC should be able to run any brushless motor to it's rated current, so that's all you'd need to replace. We can make suggestions if you want to go this route.

- Buy more props. yeah, I know you'll buy another pack, but props can be considered a consumable item when training. Buy a couple more packs than you think you need, and consider buying more.

- Buy more durable props. The DAL multirotor props have picked up a reputation as "unbreakable" -- not wholly true, but definitely more durable, enough so to justify their slightly higher cost.

- Stop breaking props. I know, easier said than done, but there are things you can do to go easy on them. Whenever it looks like the prop will touch the ground (landing, planned or otherwise) cut the throttle -- if the motor isn't forcing the prop into the ground, it's less likely to break. Also, when landing try to flare -- pull back on the elevator just as it's about to land so it stalls just as you touch the ground. This generally means the tail touches a brief instant before the nose at a shallow angle, and is a lot easier on the motor/prop/nose -- yes, this requires skill, but that's what you're working on learning ;)


As for Landing gear, how well they "work" depends. Bigger wheels do better on rougher surfaces, but they also act as a bigger source of drag, robbing power and flight time, neither of which an 1806 on a tiny trainer has a lot to just throw away. The gear itself can be . . . troublesome to get right, but mount it north of the CG and usually you can dink with it enough to get it to work. Too far aft and it'll tip over on takeoff and landing (which is entirely what you're trying to avoid), and too far forward affects ground handling and makes balance on the airframe difficult.

. . . not to mention the low airframe weight on a bumpy surface makes for a bumpy ride . . .
 
#4
I am in the camp of just keep buying them until your skill level increases. The genfan especially break real easy but are really cheap and can find places like twistedquads where it gets cheaper the more packs you buy.

The smaller APC E propellers hold up better on belly landings and such but cost 4-5X more.

Whats really nice about the threaded shaft on the 1806's is it's very rugged and would take a very hard hit to bend/break the shaft.

The Suppa A1510 is a good replacement for the 1806 and you can put a prop saver on it. However the shaft is not near as rugged and more likely to bend on crashes.

So pick your poison really, buy more cheap props or replacment shafts.
 
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#5
I recently built the Ft-Tiny Trainer as well and powered it with the EMAX MT 1806 motor. I got my props from Heads Up RC (Florida) for this airplane, but I suspect they would break off on landing, possibly bending the motor shaft. So, I am thinking about coming up with a lightweight landing gear for it. It is to cold and the ground is now snow covered here in Michigan, so I have some time to come up with a landing gear design. Looks like a fun flyer, regards, PaperAirplane
 

GLuft3

Junior Member
#6
Thanks for all the helpful replies! I guess I'll just continue to invest in props. They're not that expensive. Seems easier than gunking the Trainer up with appendages.

Between that--and more time on the simulator--we should be in good shape.
 
#7
I recently built the Ft-Tiny Trainer as well and powered it with the EMAX MT 1806 motor. I got my props from Heads Up RC (Florida) for this airplane, but I suspect they would break off on landing, possibly bending the motor shaft. So, I am thinking about coming up with a lightweight landing gear for it. It is to cold and the ground is now snow covered here in Michigan, so I have some time to come up with a landing gear design. Looks like a fun flyer, regards, PaperAirplane
I get most of my stuff from HeadsUp as well. Very fast and reliable shipping. What prop are you using? I am using the GWS 7060 prop. I tried the 6030 prop they have and I just couldn't generate enough thrust for the Tiny Trainer. Even with a 7060 prop and 2s battery I'm getting really modest thrust.

I think one thing about the prop saver in my case is that I am losing thrust because of a slightly loose connection. Some of the guys at the field seem to think it's fine but I think I'm losing thrust.

I'm still trying to find the sweet spot with the mini in terms of motor, prop, battery combo.
 

Craftydan

Hostage Taker of Quads
Staff member
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#8
I suspect a 7x6 prop would bogging down badly on an 1806 2200-ish KV motor, even running on 2S. Run too long/too steep of a prop (I expect a 7x6 is both on that motor) and the motor lacks the power to spin the prop fast enough to get the prop into an efficient region . . . and instead of thrust, it beats the air :(

If you're wanting to milk more out of that motor, I'd recommend either SEVERELY dropping the pitch as low as you can find -- pitch gives you higher top speed, at the cost of less thrust at low speed -- and consider moving up in voltage (and WAY down in prop as the voltage goes up -- higher voltage -> higher RPM -> higher power demand for the same prop).

As for the prop saver . . . not really -- so long as the band holds the prop tightly, when the prop speeds up, it will shift counter-turn a bit more against the bands and stop. the only places where this is an issue is near breaking point (stay under 100W) or if you need fine control of throttle, like a multirotor. on a fixed wing, it's just not an issue if the power is low enough.

. . . but the whole point of this thread is the 1806 multirotor motors don't have prop savers . . . are you sure you're using the same motor?
 
#9
5mm threaded shaft prop savers

Do you think that if a prop saver style adapter were made for using these multi-rotor motors on FT planes or other similar styles that it would work. I use prop savers on my rimfire 250 with 8x3.8 sf props. I'd like to be able to use these on 2205-2300 kv motors, especially on the FT arrow to limit prop consumption. I'm just thinking getting a batch of these milled likely wouldn't be so hard to do.
 
#11
I have access to a lathe and was just wondering if it would be worth spending my time to try this out. In theory their really isn't much too these just bring it down to size on the prop end and drill and tap the other end.